孔隙度反演回剥法在储层物性定量预测中的应用:以珠Ⅲ坳陷文昌区为例

Application of Porosity Inversion Method to Reservoir Quantitative Prediction:Taking Wenchang Area in Zhu Ⅲ Depression as an Example

储层孔隙度演化定量研究可以揭示实际孔隙度演化过程,为油气勘探靶区优选提供指导。利用埋藏演化史、热史分析及流体包裹体等资料,结合储层成岩特征,建立了文昌凹陷流体-成岩演化序列,包括4个阶段:第一阶段(初始沉积至28Ma),地层流体为中-偏弱酸性,发生压实作用,形成少量黄铁矿;第二阶段(28～21 Ma),地层流体为酸性,发生长石溶解、石英加大及自生高岭石沉淀;第三阶段(21～5.3Ma),地层流体为碱性,发生石英颗粒及其加大边的溶解、碳酸盐胶结,该阶段在18.5～18.3Ma和15～8.3Ma期间发生了2期油气充注;第四阶段(5.3Ma至现今),地层流体为酸性,发生第二期酸性溶解。以该成岩演化序列为约束,结合面孔率-孔隙度之间的转化关系,确定了各期成岩作用对储层孔隙度的贡献量,进而恢复了各地质历史时期的真实孔隙度。在此基础上建立了不同岩性、不同胶结物含量以及现今不同埋深下的孔隙度演化预测图,将控制储层物性演化的微观参数转化为宏观模型,该预测图进一步明确了文昌A凹陷珠海组低渗"甜点"储层控制因素,提高了储层预测的准确率。本次研究证实在成岩演化序列约束下,孔隙度反演回剥法可以实现储层物性的定量预测,对油气勘探开发具有重要指导意义。

This paper uses burial history,thermal history,fluid inclusion data and digenetic features to build a fluid-diagenetic sequence.From initial deposition to 28 Ma,the formation fluid is neutral to slightly acidic,mainly developed with compaction and a small amount of pyrite.From 28 to 21 Ma,when the formation fluids were transformed into acid with the release of organic acids,feldspar dissolution and quartz overgrowth occurred.Subsequently,from 21 to 5.3 Ma,the formation fluids were converted into alkaline,with two phases of hydrocarbon charging and carbonate cements developed at the same time.Dating back from 5.3 Ma to nowadays,the mantle-derived carbon dioxide turned the formation fluid to acidic,with the occurrence of the second phase of the acid dissolution.Taking the fluid as a constraint,we can restore the porosity in geological history,combined with surface porosity-porosity conversion chart.On this basis,quantified prediction charts were established under different sorting and cement,which can convert the microscopic parameters of reservoir properties to macroscopic model.The forecast chart produced good results in Wenchang A Depression with a 77.8% accuracy rate.This application confirms that this method indeed has constructive significance for improving the accuracy of reservoir prediction.This study has important implications for further clarified hypotonic "dessert" reservoir controlling factors of Zhuhai Formation in Wenchang A depression to improve the accuracy of reservoir prediction.